Static discharge apparatus

ABSTRACT

Apparatus to discharge static electrical charges on the body of an aircraft, having an extended discharge range. Both a lowpotential discharge path and a parallel high-potential discharge path are provided for discharge of accumulated static charge.

United States Patent [72] Inventor William K. McLaln Orange, Calif.

[21] Appl. No. 25,155

[22] Filed Apr. 2, 1970 [45] Patented Dec. 14, 1971 [73] Assignee AliceRichmond McLaln Orange County, Calif.

[54] STATIC DISCHARGE APPARATUS 4 Claims, 3 Drawing Figs.

[52] U.S.Cl 317/2 E, 174/4 R [51] Int. Cl v; B64d 45/02 [50] Field ofSearch 317/2 R, 2

E; 217/2 E; 174/3, 4 R; 343/899 [56] References Cited UNITED STATESPATENTS 2,933,732 4/1960 Tanner 343/899 3,106,663 10/1963 Tanner...317/2E 3,131,391 4/1964 Boswell et al. 343/899 3,528,629 9/1970 Cooper317/2 E 3,034,020 5/1962 Benkoczy et al.. 317/2 E 3,170,087 2/1965Tanner et al 317/2 E Primary Examiner-L. T. Hix

Atlorneys'George .I. Netter and Kendrick and Subkow ABSTRACT: Apparatusto discharge static electrical charges on the body of an aircraft,having an extended discharge range. Both a low-potential discharge pathand a parallel highpotential discharge path are provided for dischargeof accumulated static charge.

The present invention relates generally to static discharge apparatus,and, more particularly, to such static discharge apparatus having anextended discharge range without deleteri-' ous effects on theapparatus.

An ever present problem with aircraft is the accumulation of staticelectric charge on the aircraft during flight, which charge can, if notdissipated otherwise, discharge suddenly in the form of lightning anddestroy a part of the craft. Even'if charge dissipation means areadopted to prevent such lightning damage, they can create an undesirablylarge amount of radio noise, interfering with communications systems ofthe aircraft.

In the past static charge removal has been conventionally accomplishedby using low-potential discharge electrodes having sharp or pointed endswhich ionize the adjacent air to produce a charge dissipation path.However, in removing charge by such electrodes, high fronts aredeveloped and radio communications arefrequently impaired. For thisreason, an alternate approach in the past has been to construct staticdischargers of brushlike electrodes consisting of a plurality of smallfilamentlike elements which effect discharge of lower levels ofaccumulated charge, thereby preventing accumulation of charge to thatstate at which its discharge would either be deleterious to the aircraftor interfere with radio communication. The brush electrodes, however,although excellent for low-charge, ranges (i.e., 25 kilovolts or under),can be destroyed or substantially impaired very quickly if a highermagnitude of charge is developed on the aircraft.

SUMMARY OF THE INVENTION In accordance with the practice of thisinvention, there is provided a rodlike, low-resistance element, one endof which is connected to an external part of the aircraft and its outerend terminates in a spherical electrode of predetermined dimensions.Spaced from the spherical electrode there is provided a brushlikeelectrode affixed to the rodlike element the brush element parts ofwhich are arranged in surrounding relationship to the rodlike element.Thedimensions and spacing of the spherical electrode and the brushelectrode are such that the brush electrode will afford dissipation oflower-charge ranges of accumulation, whereas on high-chargeaccumulation, dissipation will be effected via the spherical electrode,thereby preventing damage to the brush electrode.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of the staticdischarger of the present invention.

can be considered as having zero resistance. Similarly, the ballelectrode 12 afiixed to the end of the rod 11 is constructed of alow-resistance metal. In a practical construction of the invention, therod 11 was approximately 5 inches in length and FIG. 2 is a longitudinalsectional view of the static discharger of FIG. I, taken along the line2-2 of FIG. 1.

FIG. 3 depicts the static discharger in disassembly.

DESCRIPTION OF A PREFERRED EMBODIMENT Turning now to the drawings andparticularly FIG. 1, the static discharger device of the presentinvention is identified generally by the reference numeral 10 and isseen to include a rodlike element 11 terminating at its outer end in aspherical ball electrode 12, the other end of which is received within amounting means 13 to be afiixed to the aircraft. The rod 11 andspherical electrode 12 generally comprise the high-voltage dischargemember, that is, the means by which accumulated charge on the aircraftin excess of approximately 25 kilovolts is dissipated.

Additionally, a brushlike low-voltage electrode means 14 is affixed tothe member 11 at a point spaced from the spherical electrode 12 with thebrushes flaring outwardly toward the ball end.

As to details of construction, the rod 11 consists of a good conductivemetal such that its total resistance measured from one end to the otheris very low, and, for all practical purposes had a diameter of about0.050 inches. The spherical electrode 12, affixed to the outer end ofthe rod 11, had a diameter of approximately 0.250 inches. The relativedimensions specified for the members 1 l and 12 are important in thatthe discharge effect to be achieved via the rod 11 and the electrode 12into the surrounding air is for relatively high levels of static chargeaccumulated on the aircraft, i.e., in excess of approximately 25kilovolts. If the ball member 12, for example, has a substantiallysmaller diameter, it will tend to discharge lower levels of accumulatedcharge, thereby making it inherently subject to damage in the event thatit would have to dissipate a much higher level of voltage. ON the otherhand, if the diameter of the ball 12 is made substantially larger,although it will then easily accommodate discharges ofhigher-levelvoltages, this will permit an undue accumulation of highvoltage on the aircraft which could discharge via the low-voltageelectrode means to be described later herein and damage it.

More particularly, the potential difference at which corona willdevelopor discharge of an accumulated charge on a conductor to, say, asurrounding air environment, is directly related to the surfacecondition of the conductor. That is, wherever a sharp point or edgeexists, corona and its discharge will take place at a relatively lowpotential, whereas for very smooth flat or slightly curved surfaces, thecharge potential necessary to achieve corona is much higher. Forexample, in the specific embodiment given above for a 0.250 metalsphere, breakdown to achieve discharge requires approximately 25kilovolts. Also, the materials used are important in that the workfunction of the material determines the number of electrons that can beprovided by the material for producing corona.

The low-voltage discharge electrode 14 includes a connecting collar 15affixed onto the rod 11 at a point spaced inwardly of the ball electrode12. A plurality of flexible conductive brushes I6,one end of each beingsecured in the collar and the other end extending toward the ballelectrode; as depicted in FIGS. -1 and 2, the brushes l6 flare outwardlyin a cone, which is the shape they will assume during charge dissipationdue to mutual repulsion of the like charges carried by the brushes.However, when in an uncharged condition the flexible brushes will tendto be relaxed and extend randomly about the rod 11.

The holder or attachment means 13, as shown best in FIG. 3, comprises apair of cast body halves l7 and I8 with as included slot 19, into whichthe rod II is fittingly received when assembled. Although othermaterials may be found satisfactory, best results to date have beenobtained by constructing the body halves l7 and 18 from plastic andplating the outer surfaces of the halves with a good conductor such asnickel or gold, for example.

As seen best in FIG. 2, the end of the rod 11, received I within slots19 of the body halves l7 and 18, is slightly enlarged as at 20.Moreover, the slots 19 include a quantity 21 of an epoxy material, forexample, filled with a conductive powder such as silver. The material 21not only serves to anchor the rod within the slots 19, but also insuresgood electrical contact between the rod 11, the plating of the bodyhalves l7 and 18, and the aircraft. The means 13 may be connected to theaircraft by any conventional technique, a threaded member 22 beingillustrated as exemplary of but one such means. I claim: 1. Apparatusfor discharging static electric charge from a body into a gaseousenvironment, comprising:

a metal rod; electrically conductive means connecting one end of the rodto the body and disposing the other rod end in the gaseous environment;a smooth surfaced metal ball affixed to the other rod end;

and

a plurality of metallic filament means, each having one end mountingmeans providing a low-ohmic connection electrically connected to the rodinwardly of the ball and I between said wing and said rod; extendingaway from aid rod to terminate in the atan electrode connected to theother end of said rod having a mosphere. smooth curved outer surface;and 2. Apparatus as in claim 1. in which metallic collar means 5 a p ityof elongated elements. h h ing ne en are received onto said r d d fi' dthereto at a point physically and electrically connected to said rod andthe spaced inwardly of the metal ball, said metallic filament meansOthef end "8 Pointed and extending y from Said being secured to saidcollar means. Int he an:-

3. A static electric charge discharger for attachment to the A Stat":deem: charge dlschal'ger as clalm which wing f aifcrafl'comprisingz 10the mounting means includes a pair of parts that are fitted a l itogether about the rod end, the surfaces of said parts being mountingmeans affixed to the aircraft wing having parts for coated wnh aconductwe securingly receiving one end of the rod therein, said

1. Apparatus for discharging static electric charge from a body into agaseous environment, comprising: a metal rod; electrically conductivemeans connecting one end of the rod to the body and disposing the otherrod end in the gaseous environment; a smooth surfaced metal ball affixedto the other rod end; and a plurality of metallic filament means, eachhaving one end electrically connected to the rod inwardly of the balland extending away from said rod to terminate in the atmosphere. 2.Apparatus as in claim 1, in which metallic collar means are receivedonto said rod and affixed thereto at a point spaced inwardly of themetal ball, said metallic filament means being secured to said collarmeans.
 3. A static electric charge discharger for attachment to the wingof an aircraft, comprising: a metallic rod; mounting means affixed tothe aircraft wing having parts for securingly receiving one end of therod therein, said mounting means providing a low-ohmic connectionbetween said wing and said rod; an electrode connected to the other endof said rod having a smooth curved outer surface; and a plurality ofelongated elements, each having one end physically and electricallyconnected to said rod and the other end being pointed and extending awayfrom said rod into the air.
 4. A static electric charge discharger as inclaim 3, in which the mounting means includes a pair of parts that arefitted together about the rod end, the surfaces of said parts beingcoated with a conductive material.